A smart key for a vehicle can unlock a lock of the door or the trunk of the vehicle and can start an engine via bidirectional communication, when a user only carries the vehicle smart key. The vehicle smart key uses an immobilizer function and a unique cryptogram, whereby vehicle theft is prevented and convenience may be provided.
The vehicle smart key can provide a function of a certain user authentication device (theftproof), and can start an engine after system authentication. The vehicle smart key can perform a door/trunk lock control function, an alarm function, an engine start function, or the like at a long distance (e.g., about 30 m) using the smart key. The vehicle smart key may recognize proximity (e.g., about 5 m) between the vehicle and the smart key using short-range communication, and can automatically unlock the door and start the engine of the vehicle.
An existing vehicle smart key has provided a smart key function basically using two wireless frequency signals, such as a low frequency (LF) signal and an ultra high frequency (UHF) signal. For example, the smart key uses an LF antenna to recognize a short-distance and uses a UHF antenna to recognizes a long-distance, in performing a smart key operation.
When it is desired to operate a vehicle smart key by including the vehicle smart key in an electronic device (e.g., a portable phone), the way of installing an antenna in consideration of the limited space in the electronic device and the way of securing performance after the installation of the antenna need to be considered. In order to install the existing smart key function in the portable terminal, a UHF antenna and an LF antenna need to be installed in the portable terminal. From the perspective of the structure and the size of a terminal, it is very difficult to prepare a space for the installation of the LF and UHF band antennas in the terminal. Particularly, the vehicle smart key uses the LF and UHF band antennas. Conversely, the electronic device mainly use a GHz band antenna. Therefore, it may be difficult to install the antennas of the vehicle smart key in the electronic device. Also, although the antennas can be installed in the electronic device, it is difficult to secure the desired performance using the corresponding antennas. For example, when a smart key is installed in the electronic device, performance may deteriorate according to various conditions, such as a way that the electronic device is held, the location of the electronic device, or the like due to the characteristics of the electronic device. Also, there is desire for a method of avoiding the deterioration in the performance.